<!DOCTYPE html>
<html>
<head>
    <title>Bootstrap 实例</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/css/bootstrap.min.css">
    <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script>
    <script src="https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js"></script>
    <script src="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script>
</head>
<body>

<div class="container mt-3">
    <h3>输入框组</h3>
    <p> .input-group .input-group 类来向表单输入框中添加更多的样式，如图标、文本或者按钮，.input-group-prepend 类添加在前面，.input-group-append 添加在后面。</p>
    <p>使用 .input-group-text 类来设置文本的样式。</p>

    <form action="/action_page.php">
        <div class="input-group mb-3">
            <div class="input-group-prepend">
                <span class="input-group-text">@</span>
            </div>
            <input type="text" class="form-control" placeholder="Username" id="usr" name="username">
        </div>

        <div class="input-group mb-3">
            <input type="text" class="form-control" placeholder="Your Email" id="mail" name="email">
            <div class="input-group-append">
                <span class="input-group-text">@runoob.com</span>
            </div>
        </div>
        <button type="submit" class="btn btn-primary">Submit</button>
    </form>
</div>


</body>
</html>